The present invention relates to a thermoexpandable microcapsule, production thereof and a method of expansion.
It was described in Japanese Patent Publication No. 42-26524 a process of production of a thermoexpandable microcapsule by microencapsulating with a thermoplastic polymer a volatile expanding agent which can be vaporized at a lower temperature than the softening temperature of the thermoplastic polymer.
There are many cases that a thermoexpandable microcapsule having a heat resistance and a chemical resistance is required in use thereof. As such microcapsules a thermoexpandable microcapsule excellent in heat resistance and chemical resistance and a microcapsule excellent in heat resistance have been disclosed in Japanese Patent KOKAI No. 62-286534 and Japanese Patent Application No. 4-95174 respectively.
In order to obtain a thermoexpandable microcapsule having a high heat resistance and chemical resistance the temperature for expanding of the microcapsule must be heightened. However, when such a microcapsule is expanded, it is often heated to expand after mixed with a binder resin and the like or coated depended on the purpose of use, and it is not preferable that such a mixture is excessively heated at expanding.